Field of the Invention
Embodiments of the invention generally relate to oil well stimulation and compositions for the stimulation of hydrocarbon bearing, heavy oil containing formations, deep oil reservoirs, and tight oil reservoirs. More particularly, embodiments of the invention relate to enhanced oil recovery methods and compositions for stimulating a hydrocarbon-bearing, heavy oil containing formation, a deep oil reservoir, or a tight oil reservoir, whereby exothermic reactants are utilized to generate in-situ steam and nitrogen gas downhole in the formation or the reservoir as an enhanced oil recovery process.
Description of the Related Art
The recovery of unconventional hydrocarbons such as heavy oil is receiving great interest, as world energy demand increases along with global oil prices. Producing such high viscosity oil is complex and challenging, and usually requires chemical or thermal techniques.
One commonly employed technique for increasing the extraction of heavy oil from the oil reservoir is steam injection. Steam injection is considered an enhanced oil recovery process that uses thermal energy to stimulate the oil reservoir. Examples of conventional steam injection processes include, for example, cyclic steam stimulation and steam flooding.
Conventional cyclic steam stimulation includes three stages: injection, soaking. and production. Steam is first injected into the well for a specified amount of time to heat the oil in the surrounding reservoir to facilitate the flow of the oil. After injecting a specified amount of steam, the injected steam remains in the reservoir to “soak” for another specified amount of time (e.g., typically a few days). The “soaking” steam generates increased pressure in the reservoir, forcing oil to flow from the well. Subsequently, oil is produced from the well using artificial lift (e.g., mechanical extraction of the oil from the reservoir).
Steam flooding is another conventional steam injection process, whereby the heavy oil in the reservoir is heated to high temperatures to decrease the viscosity of the oil, causing the oil to more easily flow through the formation toward the producing wells. Conventional steam flooding relies on constructing a steam generating plant and injecting steam at a well head. Disadvantages of conventional steam flooding systems include high initial capital costs (e.g., associated with the steam generating plant), high operational cost, and heat loss due to distance from generators to downhole, which make conventional steam injection processes ineffective for recovering oil from deep oil reservoirs. Moreover, existing steam flooding systems are applicable for off-shore oil reservoirs, and are inapplicable for off-shore ones.
Because conventional steam injection processes have limited effect for stimulating hydrocarbons from deep heavy oil containing formations, off-shore formations or tight oil reservoirs with high operational cost, what is needed are enhanced oil recovery methods and compositions for the thermal recovery of hydrocarbons from deep heavy oil formations, off-shore, on-shore or from a tight oil reservoir, which require less initial capital costs and minimize the operational cost and heat loss in pipelines that are commonly present with conventional steam flooding processes.